MISMARPE protocol: minimally invasive surgical and miniscrew-assisted rapid palatal expansion

ABSTRACT Objective: The purpose of this article is to present the MISMARPE technique, a new minimally invasive surgical procedure to treat maxillary transverse atresia in adult patients under local anesthesia and on an outpatient basis. Technique description: The technique consists of miniscrew-assisted rapid palatal expansion (MARPE) associated with a minimally invasive approach using maxillary osteotomies, latency and activation periods until the desired expansion is achieved. The present MISMARPE technique was performed in 25 consecutive cases with a success rate of 96%, yielding good skeletal outcomes with minimal trauma. The expander appliances, with their anchorage types, and a description of the surgical steps of the MISMARPE technique are presented. Conclusion: MISMARPE is a new and effective alternative for less invasive treatment of maxillary transverse deficiency in adults, compared to conventional surgery. Emphasis is placed on the importance of systematic and well-established protocols, for executing the procedures safely and predictably.


INTRODUCTION
Maxillary transverse deficiency is a common dentofacial deformity, often associated with dental crowding, narrowing of the palate, and crossbite.Maxillary atresia, with varying degrees of severity, can have significant functional repercussions. 1 Conventional orthopedic expansion or rapid maxillary expansion (RME) is the treatment of choice for cases involving young patients with growth potential, i.e., those without complete maturation of the midpalatal suture.In such cases, the use of appliances like Haas or Hyrax can yield substantial transverse gains, correcting the existing transverse discrepancy. 2r skeletally mature patients with significant maxillary atresia, where dentoalveolar compensation is not recommended, the RME procedure is ineffective, due to the substantial resistance of the circummaxillary sutures to opening.The solution in these cases was extensive surgical procedures involving weakening the resistance pillars through osteotomies, 3,4 a surgical technique known as surgically-assisted rapid palatal expansion (SARPE).This intervention must be performed in a hospital setting, under general anesthesia, and is considered a procedure with higher morbidity and costs. 5,6Another treatment option would be the transverse correction using orthognathic surgery, with segmental osteotomy (segmented Le Fort I osteotomy -a variation of the classic Le Fort I maxillary osteotomy), 7,8 allowing a transverse correction of up to 7mm.
Dental Press J Orthod.2024;29(3):e24spe3 The patients benefit by undergoing only one procedure under general anesthesia for the total correction of their deformity (transverse, anteroposterior, and vertical).However, in some patients, the presented transverse deformity does not allow for adequate treatment with maxillary segmentation alone, necessitating a more significant pre-maxillary expansion.
The Minimally Invasive SARPE was conceived to reduce surgical morbidity, and align with contemporary orthognathic surgery concepts.This technique was published by Hernández-Alfaro et al. 9 in 2010, and consists of performing an outpatient surgical expansion under local anesthesia and intravenous sedation using a minimally invasive access in the maxilla.This corresponds to an incision of the mucosa extending from the lateral incisor to the lateral incisor (radically smaller surgical access than in the conventional SARPE).
Both SARPE techniques, conventional and minimally invasive, are performed with orthodontic devices, such as the Hyrax type, using dental anchorage.However, some dental complications, bone resorption, and relapses are reported with this type of anchorage, especially in more mature patients. 10,11e use of skeletal anchorage devices to assist in the treatment of maxillary atresia, known as miniscrew-assisted rapid palatal expansion (MARPE), was also first published in 2010. 12 this technique, transverse expansion occurs by means of Dental Press J Orthod.2024;29(3):e24spe3 skeletal anchorage, assisted by bicortical mini-implants in the palate, anchoring the expander appliance.Since then, the MARPE procedure has gained popularity and been extensively studied, demonstrating successful results when well indicated, with significant skeletal gains due to bone anchorage.
However, the evidence found in the literature is still mainly related to young adults, no older than the fourth decade of life, [13][14][15][16][17][18][19] with isolated reports of cases at an older age. 20,21e Minimally Invasive Surgical and Miniscrew-Assisted Rapid Palatal Expansion (MISMARPE) was first published in 2022, 22 after several years of research. 23The technique was developed to target adults with maxillary atresia, combining the concepts of minimally invasive surgery with skeletal anchorage (MARPE), aiming to achieve maxillary expansion in adults with a reduction in surgical morbidity and patient costs.

MISMARPE -ANCHORAGE AND APPLIANCE TYPES
The MISMARPE technique is performed with expander appliances, using two types of anchorage: bone-borne (purely skeletal anchorage) and tooth-bone borne (also called hybrid anchorage, as it uses both dental and skeletal anchorage), as illustrated in Figure 1.The appliance consists of an expander screw (which can have different dimensions, according to the maxillary atresia) positioned on the palate with four bicortical miniscrews, two in the anterior region and two in the posterior region.The expander screw has a fixation bar that will be welded to the molar bands.The expander screw and the miniscrews are similar for both types of anchorage, maintaining the same minimally invasive osteotomy surgical protocol.In cases of exclusively skeletal anchorage, the fixation bar should be removed.The following sections will address the clinical and laboratory steps for fabrication, indications, advantages, and disadvantages of these two anchorage types, as well as a description of the surgical steps of the MISMARPE technique.an intraoral scanner and imported as STL files (a file format used to represent 3D models in computer graphics, originating from "stereolithography" or "standard tessellation language").

A
An STL file of the expander screw is also required.The first step is to orient the 3D tomographic image to standardize the head position from the Frankfurt plane (Or L-Po-Or R) parallel to the axial plane.The Nasion-Anterior Nasal Spine plane should be perpendicular to the Frankfurt plane (Fig. 2).

TOOTH-BONE-BORNE ANCHORAGE
Tooth-bone borne anchorage, or hybrid expanders, feature skeletal anchorage using four parasutural mini-implants associated with bands cemented to the molars.The miniscrews are positioned to the body of the expander screw, while the wire extensions of the screw are welded to the bands of the first molars.
The protocol for determining the positioning of the tooth-boneborne expander screw can be performed with or without a guide.
The following step-by-step process will detail the selection of the expander screw size and positioning, as well as the size of the miniscrews without the help of the positioning guide.Adjustable extensions allow the miniscrews to be positioned close to the palate in patients with severe maxillary atresia.
This screw is available in sizes 9, 11, or 13mm (Fig. 4). it should be allocated to a region of the palate with sufficient bone quantity.The "T" zone is interesting, due to the available alveolar bone and cortical thickness. 24,25This region is generally located in the parasutural region and the region of the third palatal rugae (Fig. 5).Therefore, the positioning of the anterior miniscrews should coincide with the third palatal rugae, equidistant from the midpalatal suture (3-mm distance on both the right and left sides).The posterior miniscrews should be positioned according to their respective template -about 15mm distal, according to the type of expander screw used (PecLab, Belo Horizonte, Brazil).The first step involves transferring the anterior miniscrew positions, as defined in the working model, to the CBCT, in the axial slice.From this anteroposterior position, measure 3mm on each side of the midpalatal suture.At these points, in a sagittal slice, measure the bone thickness (from the nasal cortical to the palatal cortical) and the thickness of the palatal mucosa.
Add 1mm to this measurement, referring to the distance from the expander appliance to the palate (if the expander has more than 1mm of separation from the palate, this distance should be considered in the total), and add the thickness of the expander body (2mm).It is suggested that the miniscrew size be chosen closest to the sum of these distances.The definition of the posterior miniscrew size follows the same protocol: measure the distance between the anterior and posterior holes, according to the template -in this case, 15mm distal.Figure 6 illustrates the steps of choosing the miniscrew size using the CBCT.
» Installation of the expander appliance: The bands of the expander appliance should be cemented to the upper first molars (Fig. 7).Thus, in this protocol, the expander appliance serves as a guide for installing the miniscrews.The installation can be performed by the orthodontist, immediately after the cementation of the expander; or by the oral and maxillofacial surgeon, at the same time of the MISMARPE protocol.The superimposition is based on the best fit of teeth in the axial, sagittal, and coronal planes (Fig. 8).The superimposition is saved, and the overlay tool is closed.After this step, the STL file of the expander screw is added and positioned at the desired location, respecting approximately 1.0 mm of distance from the contour of the palatal mucosa, using the file addition and positioning tool (Fig. 9).The miniscrews

RECOMMENDATIONS AND CARE
Inflammation of the palatal mucosa can destabilize the miniscrews and potentially cause procedure failure.Therefore, patients should be instructed regarding oral hygiene care.
In addition to regular brushing, water jets should be performed using a 5 or 10ml syringe, directing the water jet between the expander and the palatal mucosa.Patients should also be advised to avoid hard and sticky foods (such as candies and chewing gum).The patient should apply 0.2% chlorhexidine digluconate gel twice a day, with the help of a brush.
After installation of the expander appliance, the surgical phase of the procedure is carried out.

PREOPERATIVE
The MISMARPE technique was designed to be performed in an outpatient setting, under local anesthesia, and without sedation assistance.However, for patient comfort, if necessary, an anxiety control protocol can be implemented, with the oral administration of a benzodiazepine for conscious sedation, 30 minutes before the surgical procedure, or intravenous sedation performed by an anesthesiologist.

TECHNIQUE -STEP BY STEP
The oral cavity is antiseptically cleansed with 0.12% chlorhexidine, and sterile fields are set up for the surgical procedure.
Local anesthetics are administered, using a potent anesthetic with a vasoconstrictor (typically, 4% articaine with 1:100,000 The minimally invasive approach is performed through a mucoperiosteal incision in the anterior vestibular region of the maxilla, 3 mm above the mucogingival line.The surgical access averages 1 cm, extending from central incisor to central incisor (Fig. 12A).Subperiosteal detachment is then performed in the nasomaxillary region, without invading the nasal fossa and without detaching the musculature inserted into the anterior nasal spine, only accessing the entrance of the piriform aperture in its lower lateral portion on the left and right sides, and finally creating a tunnel-like detachment to the posterior region of the maxilla, bilaterally (Fig. 12B).The first osteotomy, called subspinal osteotomy, is performed at the anterior nasal spine.The anterior portion of the nasal mucosa is then detached from the nasal floor with a periosteal elevator (Fig. 13A, B).Afterward, a vertical osteotomy is performed in the midline between the central incisors, corresponding to the midpalatal suture, covering the vestibular and palatal bony cortical bones (Fig. 13C, D).Both osteotomies are carried out using piezoelectric technology.Finally, a horizontal osteotomy of the maxilla is performed with a reciprocating cutting saw or piezoelectric tip.The region is visualized through the previously detached mucosal tunnel, with the help of the retraction of the vestibular mucosa.Thus, the cutting saw, or the piezo tip, is positioned in the posterior region at the level of the zygomatic pillar, just above the dental roots, and the medial walls of the maxillary sinuses are cut as the cutting saw progresses medially, up to the piriform aperture (Fig. 14A, B).The total extent of the cut is slightly oblique, with a more posterior lower inclination and a more anterior upper inclination, always respecting the limit above the dental roots.
The same osteotomy is performed on the right and left sides, following the same criteria (Fig. 14C, D).
The MARPE expansion device is then activated until a small diastema between the central incisors is visualized.This step is essential to check the fragility of the bone resistance zones, especially in the midline (Fig. 15).Subsequently, the expander screw is closed again.
After reviewing hemostasis and abundant irrigation with saline solution, the operative wound is sutured.Single isolated stitches or continuous sutures can be performed using absorbable or non-absorbable suture thread (Fig. 16).The MARPE device remains inactivated for 7 days, corresponding to a latency period.After this first week, the patient returns for clinical evaluation with the surgeon and suture removal.
Subsequent follow-ups will continue with the orthodontist, for ongoing treatment.

TECHNICAL CONSIDERATIONS
The MISMARPE surgical procedure, as described here, is the The expansion screw activation should start 7 days after surgery, following a latency period.After this initial 7-day period, the activation protocol begins with a quarter turn in the morning and a quarter turn at night (equivalent to a quarter turn every 12 hours).This activation pattern continues until the detection of a midline diastema (typically occurring between the second and third day).Afterward, the activation continues with a quarter turn per day (a quarter turn every 24 hours) until the desired transverse correction is achieved.
Once the desired expansion is reached, activations are interrupted.For safety, the screw can be stabilized with a 0. The diastema obtained immediately after expansion is broad

IMMEDIATE RESULTS ACHIEVED WITH THE MISMARPE TECHNIQUE
The After MISMARPE, with an average opening of the expansion screw of 7.78mm, there was a significant increase in all linear dental, alveolar, and skeletal transverse measurements. 27The anterior region of the maxilla showed more significant increases than the posterior region in all transverse and axial measurements assessed.Dental and alveolar measurements achieved greater transverse gains than skeletal measurements in the anterior and posterior regions. 27The result was a trapezoidal opening pattern, when observed in the coronal plane; and a "V" shape, when observed in the axial plane. 27Data regarding the average response after 7.78mm of activation are presented in Table 2 and Figure 18.An advantage of the MISMARPE technique over MARPE is its predictability in treating maxillary transverse deficiency in mature patients; and, as a disadvantage, the need for osteotomy assistance, along with increased costs and factors inherent to surgical procedures.To date, there are no reliable guidelines to predict the success of skeletal expansion in mature patients. 20us, the clinical attempt of orthopedic expansion is the only reliable method to confirm the possibility of sutural opening. 20th the MISMARPE technique, patients perceive the surgical procedure as less invasive, probably due to the absence of hospitalization and general anesthesia, coupled with shorter operating times and reduced incisions. 23All these factors contribute to patients' better acceptance and tolerance of the MISMARPE procedure.
Dental Press J Orthod.2024;29(3):e24spe3 The efficacy and stability of SARPE and its indications are widely reported in the literature.Adults with maxillary atresia are candidates for SARPE, and now, also for MISMARPE. 34The main benefits of MISMARPE over SARPE include not requiring hospitalization or general anesthesia, presenting lower costs for patients, insurance plans, and the government public health policies.
Despite the excellent prognosis of MISMARPE in adults, 23,27 Thus, the present article aims to present the protocol of the MISMARPE technique, with different types of appliances (bone-borne or tooth-bone-borne anchorage), describing the surgical technique and main results obtained.Dental Press J Orthod.2024;29(3):e24spe3 Cone Beam Computed Tomography (CBCT) is necessary for planning the appropriate location of the expander appliance and miniscrews.The Digital Imaging and Communications in Medicine (DICOM) images obtained are used for the 3D image reconstructions.Dolphin Imaging software (Dolphin Imaging & Management Solutions, Chatsworth, California, USA) was used to plan the cases described in this article.Intraoral scans of the upper arch and the patient's palate should be acquired with

Figure 1 :
Figure 1: Images of bone-borne (A) and tooth-bone-borne (B) appliances used for performing the MISMARPE.

Figure 2 :
Figure 2: Orientation of the three-dimensional model from CBCT.The horizontal red line represents the Frankfurt plane, and the vertical red line represents the Nasio-Palatal line.

Figure 3 :»
Figure 3: Separation (A) and bands selection (B) for the anchoring teeth of the toothbone-borne expander.(C) Transfer molding and obtained dental cast working model (D).

Figure 4 :»
Figure 4: Positioning of the MARPE SL (A) and MARPE EX (B) expanders (PecLab, Belo Horizonte, Brazil).The adjustable extensions of the MARPE EX allow proper positioning of the expander and miniscrews in patients with extremely atresic palates.

Figure 5 :
Figure 5: Template of the expander screw (PecLab, Belo Horizonte, Brazil) positioned in the "T" zone, recommended for installing the miniscrews.

Figure 6 :
Figure 6: A) Definition of the anterior miniscrews position from the axial slice, considering the initially proposed marking on the working model.B) In the coronal slice, position the cursor 3mm away from the midpalatal suture, to select the miniscrews on the right and left sides.C) Sagittal view obtained to select the anterior miniscrews on the right side.D) Measurement of bone thickness, considering bicorticalization.E) Measurement of the palatal mucosa thickness.F) In this case, at a distance of 15mm distal, define the size of the posterior miniscrew.G) Measurement of the bone thickness of the posterior miniscrew on the right side, considering bicorticalization.H) Measurement of palatal mucosa thickness of the posterior miniscrew on the right side.I) To define the size of the miniscrew, add 1mm of palatal mucosa clearance + 2mm of expander thickness.J) Sum of distances for the selection of the right anterior and (K) right posterior miniscrews.

Figure 7 :
Figure 7: A) MARPE expander cemented.B) Installation of the miniscrews.In detail (C), observe the correct positioning of the expander in relation to the palatal mucosa, without pressure or ischemia in the region, and (D) the four miniscrews installed and well positioned in the expander holes.

Figure 8 :
Figure 8: Superimposition of the maxillary STL model file on the CBCT images ( the red line is the external contour of the model ): A) right sagittal view; B) left sagittal view; C) coronal view; D) axial view; E) three-dimensional reconstruction, with the final position of the superimposed maxillary STL model.

Figure 9 :
Figure 9: Screw positioned on the 3D reconstruction superimposed on the maxillary STL model.

Figure 10 : 20 Dental»Form 2 ;
Figure 10: Measurements of the length of the miniscrews: A and B) anterior miniscrews; C and D) posterior miniscrews.

Figure 11 : 22 Dental
Figure 11: A) STL file of the upper arch with the screw virtually positioned B) Bone-borne appliance positioned.A B epinephrine): blocking of the posterior superior alveolar nerves, infraorbital nerves, and nasopalatine nerve, along with infiltration into the vestibular mucosa of the maxilla in the region of the upper labial frenulum, to aid in hemostasis and facilitate total mucoperiosteal detachment.The anesthetic technique is further complemented by infiltrations into the palatal mucosa in the paramedian region, where the four miniscrews of the MARPE expander will be installed.Haas Júnior OL, Matje PRB, Rosa BM, Piccoli VD, Rizzatto SMD, Oliveira RB, Menezes LM -MISMARPE protocol: minimally invasive surgical and miniscrew-assisted rapid palatal expansion Dental Press J Orthod.2024;29(3):e24spe3

Figure 12 :
Figure 12: Minimally invasive approach to the maxilla: A) incision extending from tooth #11 to tooth #21; B) subperiosteal detachment through the tunnel.A B

Figure 13 : 25 Dental
Figure 13: Subspinal osteotomy and vertical osteotomy in the midline: A, C) performing osteotomies with piezoelectric technology tip; B, D) clinical aspect after osteotomies.

Figure 14 :
Figure 14: Horizontal maxillary osteotomy: A, B) execution with reciprocating cutting saw, on the left side; C) aspect of the maxilla after horizontal osteotomy (left side); D) aspect of the maxilla after horizontal osteotomy (right side).

Figure 15 :
Figure 15: Expander screw activation in the intraoperative period: A) activation with the key; B) visualization of diastema between the upper central incisors; C) visualization of diastema and opening of osteotomy; D)aspect of vertical and horizontal osteotomies (bilaterally) after activation.
result of years of technical refinements by a surgeon and his experienced team in minimally invasive techniques.It is recommended that, for the execution of the MISMARPE, the oral and maxillofacial surgeon has the proper training to perform it safely.It is not a technique recommended for beginners, but for surgeons at a more advanced level, especially those experienced in minimally invasive orthognathic surgery.The smaller access to the maxilla provides a restricted view of the structures, so the professional must go through a learning curveMISMARPE -ACTIVATION AND RETENTIONThe required amount of expansion should be planned before the surgery, aiming to identify the actual need for transverse expansion in each case.It is crucial to consider factors that may mask the transverse deficiency, such as compensations in the lower arch (excessive lingual inclination of lower teeth) or anteroposterior malocclusions (Class II or III) that can hinder the evaluation of the real transverse discrepancy.

( 3
to 8mm), and may cause dissatisfaction to some patients (Fig 17).If necessary, resin can be added to the mesial surfaces of the teeth adjacent to the diastema (#11 and #21), ensuring a consistent separation, to enable the spontaneous return of the central incisors towards the midline during the expansion stabilization period.

Figure 17 :
Figure 17: Adult patient with transverse maxillary deficiency, before (A/B) and immediately after (C/D) undergoing the MISMARPE protocol.

Figure 18 :
Figure 18: Illustration of the linear measurements evaluated pre and post-MISMARPE in the posterior region (first molars), anterior region (canines), and incisor region (Source: modified from Piccoli 27 , 2023).
the primary indication for this technique is individuals with maxillary atresia from the fourth decade of life onwards.Another indication is for patients who have unsuccessfully undergone the MARPE technique.These individuals can be immediately subjected to the MISMARPE procedure, without expander replacement, hospitalization, or general anesthesia.CONCLUSION The development of new techniques, whether through adaptation or combination of existing procedures, to provide better results for patients is essential in Dentistry.This article aimed to present the MISMARPE technique, a new and effective alternative for less invasive treatment of maxillary transverse deficiency in adults (compared to conventional surgery) under local anesthesia and on an outpatient basis.Emphasis is placed on the importance of systematic and well-established protocols, for executing procedures safely and predictably.

Table 1 :
Sample characteristics and patient distribution according to the age range of the 24 treated cases with MISMARPE (Source: modified from Piccoli 27 , 2023).
27Data on the sample characteristics and patient distribution according to age group are presented in Table1.